. how to dynamiclayy display a web page's url ?

[Toby Inkster]

With a 404 I get a page that says "404 not found" or somesuch. With a
301 I get a page that says.... what? "Permanent Redirect"?
Yup.

And what do the clients do with that?

The browser doesn't display the 301 page it to the human (although the 301
page does exist), it just follows the redirect.